diff --git a/README.md b/README.md
index 61b0b88..fac0f9a 100644
--- a/README.md
+++ b/README.md
@@ -49,7 +49,7 @@ var pdfImage = new PDFImage("/tmp/slide.pdf", {
 });
 
 pdfImage.convertFile().then(function (imagePaths) {
-   // /tmp/slide.png 
+   // /tmp/slide.png
 });
 ```
 
@@ -87,3 +87,11 @@ var pdfImage = new PDFImage(pdfPath, {
   }
 });
 ```
+
+You can specify what file extension to use with the `convertExtension` option.
+
+```javascript
+var pdfImage = new PDFImage(pdfPath, {
+  convertExtension: "jpg",
+});
+```